INTRODUCTION: Welcome to “Speaking of Science”, the
National Institute of Mental Health presents a series of conversations with innovative
researchers working in a wide range of disciplines to pave the way for the prevention, recovery,
and cure of mental illness.
NARRATOR: We all have difficult sometimes
painful memories stored in our minds. Memories most of us are able to come to terms with,
but for some people the trauma of experiencing danger, violence, or panic can create a debilitating
disorder. What if fear memories could be rewritten? DR. LEDOUX: All of this research was based
on systemic manipulations of the brain. NARRATOR: Dr. Joseph LeDoux is a Professor
of Science at New York University and serves as Principal Director for the NIMH funded
Center for the Neuroscience of Fear and Anxiety. He is part of a team that has found a way
to block fear memories through a process called reconsolidation. During a recent visit to
the NIMH campus in Bethesda, Dr. LeDoux explained the key to reconsolidation is understanding
how memories are formed in the first place. DR. LEDOUX: Each time you form a memory your
brain begins to form that memory in a temporary way that can be interfered with if nothing
else happens. So you have to convert a temporary memory into a long term memory in order to
have that memory at some time in the future. NARRATOR: In 1999 a study from the LeDoux
team showed the ability to block the consolidation of fear memories by injecting Protein synthesis
inhibitors to stop growth of certain cells in the amygdala, the brain’s fear hub.
DR. LEDOUX: So that led Graham Nader who was in my lab at the time say well can we do the
same with reconsolidation? Which means, instead of giving the protein synthesis inhibitor
after learning and blocking consolidation, you give it after the retrieval of a previously
consolidated memory? So you form the memory, the animal now has a long term memory and
then at some point after that memory is fully established, you give the rat the tone which
retrieves the memory and then you give the protein synthesis inhibitor and then you test
the animal the next day and the memory is no longer there. It’s like a person who
goes to trial to testify about a crime and instead of testifying about what they witnessed
on that day they testify about what they read in the newspaper. Because each time you take
a memory out of a newspaper reading did, you restore it and the information gets stored as a new
memory. So the bottom line of all this research is--your memory is only as good as your last
memory. NARRATOR: Perhaps the greatest potential for
therapeutic application is with post traumatic stress disorder patients.
DR. LEDOUX: Where a patient with intrusive memories could be through the aid of a therapist
and the aid of proper manipulations such as a drug that is safe to use with humans. The
patient could be encouraged to retrieve the traumatic memory, given the manipulation and
presumably the memory will be weakened at a later point.
NARRATOR: In December, a new study was published in Nature from a larger NYU research team
that showed a drug-free method of replacing fear memories in people using exposure training.
Dr. LeDoux acknowledges ethical questions when it comes to the science of altering memories.
DR. LEDOUX: I understand why people worry about that because memories are treated as
sacrosanct; we are our memories in many ways. We have to remember who we are to be that
person from day to day. But one thing we have to realize is just how much we manipulate
memory as part of life. Every time we watch an ad for a product our memory is being manipulated,
every time a student goes to class his or her memory is being manipulated, every time
you have a social interaction with a person you try to create a good impression which
is basically a memory. Once we put it into that context the idea that you might use memory
manipulation to help people maybe doesn’t seem so malevolent.